Last Sunday afternoon, 1,928 fans attended a soccer game at RFK Stadium. Early Monday morning, what seemed like just as large a crew moved in.

Their job: setting up for the Monsters of Rock.

Billed officially as Van Halen's Monsters of Rock, today's concert will present nine hours of loud, proud rock 'n' roll featuring five bands, four of which -- Van Halen, Scorpions, Metallica and Dokken -- could probably sell out Capital Centre on their own.

More than 40,000 tickets have been sold in advance and a sellout of 55,000 is expected -- which will be much appreciated by the promoters, since this headbangers ball not only is the summer season's biggest rock tour, but also may be the most costly ever mounted. Still, at $25 a ticket -- and given the general expectation that the 2 million ticket holders expected at the total of 29 shows will spend an average of $20 each on merchandise from the tour (T-shirts are $18 to $23, hats $13, bandannas $8 and buttons $3) -- there's little danger they'll lose money on the event.

Between the time newcomers Kingdom Come step on the 350,000-pound, seven-story stage (around 1:30 p.m.) and the time Van Halen steps off (around 10:30 p.m.), RFK will rock to 100 decibels delivered by a 220,000-pound, 250,000-watt sound system. Talk about a wall of sound! Talk about megahurts!

By show's end, the 50,000-pound, 850,000-watt lighting system will have kicked in. The sound and light systems are powered by a pair of portable generators (40,000 pounds each, with another 12,000-pound generator for the gear trucks).

Maybe this is why it's called heavy metal.

It's also why Monsters of Rock had to be outdoors: Put all this in Cap Centre and you'd barely have room for 1,928 fans.

In fact, the RFK load-in represents less than a third of the Monster gear: In the four days the RFK show was being set up, Monster stages were being torn down in Miami and Tampa and trucked up to Philadelphia (where the tour stops tomorrow) and Foxboro, Mass. (where the tour show will go on Sunday after Van Halen threatened a lawsuit against the city government, which had tried to shut it down).

"They offered a date and then pulled back," says drummer Alex Van Halen, riding a limo to a midafternoon sound check at RFK yesterday. "They're worried about so many young people being concentrated in one area. They think 'heavy metal' and they picture 80,000 people who are going to come fertilize their lawn. A few years back, we got a key to the city; now we come back and they've changed the lock."

Guitarist Eddie Van Halen and bassist Michael Anthony get a good laugh out of that one. Singer Sammy Hagar (or Hagar the Horrible, as he's known in some circles) wasn't coming in until today. He's still nursing a minor fracture of the tailbone from when he slipped onstage during the very first song on the tour's opening night last Saturday.

"We're not promoting anarchy or anything," says Anthony. "It's not 'Tear the stadium up and trash the city.' It's nothing different than a football game -- people come out for nine hours and have fun."

For the past four days, though, the people working at RFK have put the fun on hold.

"We have three stages and two roofs leapfrogging around the country," says production supervisor Jim Amen early Monday morning as tons of steel scaffolding bays are being expanded from a base stage left over from the Pink Floyd concert a week earlier. (Not that anyone will notice, but the RFK stage will be a little smaller than the custom-built tour standard of 168 feet wide by 60 feet high. "Basically we built a seven-story arena inside a football stadium," Amen points out).

By midday, shirtless crews are scrambling around in the maze of towers as more and more steel is delivered by forklift crews. "I call it an erection set for adults," Amen says. A moment later, he realizes that doesn't sound right. "Erector -- that's what I meant."

Normally, Amen would start out with a 50-man crew putting in 30 hours apiece just setting up the steel frame and roof; because of the Floyd leftovers, he's been able to cut back to 30, plus the 10-man "Mountain" crew up in the scaffolds. Except for Amen, these are all locals. The B team (Blue or Bravo) comes in on Tuesday to start setting up the sound and lights; the A team (Amber or Alpha) is headed for Philadelphia, where a from-scratch Monster set will be set up.

And, Amen says, "we also have a Universal Team, which has to be at every setup, consisting of a lead rigger, a carpenter, sound and light technicians, band roadies, merchandisers ... what we have is basically a 70-man traveling circus."

Amen has brought in 14 trucks of gear, "on top of 10 trucks that Mountain has here. With the merchandising, we have close to 30 semis, plus five buses. It's an entourage it's hard to find parking spaces for. And with the generators, we're a totally self-contained unit."

"It's not that local power is bad," says sound director Albert Leccese, "but it's pretty funky in a lot of these places. They hook you up to the local service if they don't have enough power, forgetting to tell you you're on the same power as the parking lot lights, and suddenly you have problems. This avoids that kind of a situation."

By Tuesday morning, the crew has finished the steel work; at 4 p.m. comes the pre-rig call to hang all the motors and trusses for the state-of-the-art sound and lighting systems, which will start being unloaded from nine semis at 8 a.m. on Wednesday. We're talking three-level, stacked sound system here -- the first at stage level, the second exactly 13 feet 6 inches above that and a third level above that. According to Leccese, the system consists of "3,000 components {weighing 500 pounds each and containing 75,000 individual speakers} just for the main PA, and another 300 components in the stage monitor system; that's individual loudspeaker components ... It's actually a little more than 250,000 watts if you calculate 30 kilowatts of subwoofers. That would be a very conservative rating for that system."

The speakers are ramped or forked up to the stage, or sent up an elevator shaft via trolley and chain-hoist motor; the decks are soaped down so the equipment can be dragged into the best position to send out a sound "image" to all the ticket holders.

"What you try is to get a real good direct-to-reverberant ratio in the place," Leccese explains, as if everyone knows what that means. "You try and splatter your cabinets and your sound where there are people seated as effectively as possible given the constraints of a stage in a football stadium. And you've got to have enough power available so that you have enough dynamic headroom. The slapback's an acoustic phenomenon that gets a lot of help when you actually have an audience in the seats. That absorbs a lot of it. Open concrete spaces are open concrete spaces whether you're in a stadium or a Grand Canyon -- you wouldn't want to listen to that kind of echo ..."

Oh.

Actually, echo might be irrelevant with this level of sound. According to Amen, decibel levels are "venue sensitive. A lot demand that we don't exceed 94 or 95 decibels and they'll come out and meter it, tell us to turn it down. For this show the bands like it loud and if there isn't someone to say you can't exceed X amount of decibels, then they crank it up. Hey, it's a heavy metal show. I don't think we'll exceed more than 100 decibels. Don't hold me to that."

"At the house mix console we get peaks of between 110 and 116," Leccese says, "and at the back, 95 to 100 decibels. It's not painful. A lot of people associate pain with high distortion; it's a very low-distortion sound system, so what you actually put in front of the microphone comes out of the speaker."

As for whether it makes sense to put up a huge lighting system for a show that will be two-thirds over before it even starts to get dark, no one cares. It's only rock 'n' roll and I light it, as lighting designer David Davidian might say.

Davidian's crew numbers a dozen, including six men who will spend most of today suspended 24 feet above the stage with the front spotlights. There are also 20 automated spotlights (1 million candlepower each) and 15 computer-automated light trusses weighing more than 48,000 pounds altogether, most of them hanging right above the bands ("We're very aware of that," says Anthony).

The computer factor has become increasingly important in stage lighting, Davidian explains, because "it allows you to have a little more flexibility and choice. The computer allows you to make changes in the system without a lot of manual plugging and unplugging."

Wednesday night's thunderstorm and Thursday's showers are cause for concern. "When you have water, electricity and humans, it's not a good mix," Davidian points out. "When the water gets serious, we have to shut the power down, especially the heavy electrics, cover it with plastic and wait until it subsides."

The Monsters of Rock tour packs a lot of plastic.

"We work in the rain," says Jim Amen. "The only time the men aren't on the steel is if there's thunder and lightning." Nature's thunder and lightning, not Van Halen's. Otherwise "they'll just put on their rain gear and they get wet. I just finished a month with Pink Floyd and it rained at almost every setup and most of the shows. We made up T-shirts: 'Pink Flood -- Total Lapse of Sanity Tour.' "

The concert itself will go on, rain or shine.

"Our speaker cabinets are water-resistant," says Leccese, "so it doesn't matter if they stay out in the rain." The advent of cordless equipment has eliminated one safety concern and, according to Amen, "overall safety is integrated in every aspect of production design and engineering. There's at least a 3-to-1 safety margin in everything that you see in front of you, as far as structural integrity and things of that nature. The steel is rated with that safety ratio, if not more."

By 8 p.m. Wednesday, things are basically in place, including the four "gear" semis containing everything a band might want or need. Kevin Duggan, who's in charge of the Van Halen gear truck, says it contains "a huge effects rack, a spare of everything that we use. Michael Anthony uses eight basses in the show, and we have a spare for each. Michael beats the hell out of basses and sometimes it's something you can't fix as quick as a string. He might be rolling around on the ground causing internal injury to his bass guitar and I don't have time to take it apart and fix it right there.

"Eddie {Van Halen} only uses six guitars, but we have two spares for every one of those, six guitar trunks alone," Duggan says. "And Alex {Van Halen} has got a huge setup, the biggest I've ever seen -- three full drum kits built in a circle. When Alex does a solo the whole riser spins around, or he'll turn in his seat; it's pretty massive, pretty outrageous."

"It's just a logical extension of me," Alex says. "I had a problem reaching all the drums that I wanted, so I just put them all around me. The drums rotate and it's now one of the high points in my life because I never know which end's going to face forward."

Thursday at 1 p.m., the group heads for RFK for a sound check that will last one or two hours. By the time they get on stage, the band's road crew has already done all the line checks; each musician gets some solo time to set his own preferred levels. "They just come in and tweak it out," says Duggan.

"There's nothing better to do," Eddie Van Halen shrugs.

"And you'd be surprised what a couple of days of not playing can do," his brother adds. "A runner runs every day ... a musician plays everyday. I can doodle on the drumming pads all day long and it's just not the same as playing on the drums."

Van Halen, as the headlining act, gets its sound check first, says Amen. "Then we allow the four opening bands to have a little sound check, though we don't allow them the time we allow Van Halen. Just a mike check and a line check, then back to the showers. By then everything's basically done except for peripheral details like tweaking this or that, dressing the steel or painting barricades. Once the band's ready for sound check, they just walk on, plug in and let it rip."

Riding over from the Four Seasons, the Van Halens and Anthony seem quite jovial, more like the Munsters of Rock. Eddie says he saw "Big" the night before -- he liked it -- and he knows he'll be offering his own twist on convoluted adolescence today.

"The fancy hotel is management's attempt to achieve a little class in our eyes," muses Alex, sounding very unmillionaireish. "Holiday Inns would be fine. At least you know what the room is going to be like and you know room service is going to be there."

You could say the same about the Monsters of Rock.